Cold storage stabilized organophosphorus insecticide formulation and method of making same

ABSTRACT

There is disclosed a cold storage stabilized organophosphorus insecticide formulation. The formulation comprises a solid carrier and between approximately 2% and 40% by weight of the ultimate formulation of a nominally solid organophosphorus insecticide and between approximately 0.5% and 10% by weight of the ultimate formulation of a stabilizer compound selected from cyclohexanone and N-methylpyrrolidone. A method of making the cold storage stabilized organophosphorus insecticide formulation is also disclosed.

FIELD OF INVENTION

The present invention relates generally to insecticides, and, morespecifically, to cold storage stabilized organophosphorus insecticideformulations. The present invention also relates to a method of makingcold storage stabilized organophosphorus insecticide formulations.

BACKGROUND OF THE INVENTION

Organophosphorus compounds are well known in the art as agriculturalinsecticides. Organophosphorus compounds have been formulated both asliquid and as solid products. The solid formulations have been sold asboth powders and granules; however, the granular form is most commonlyused today.

Organophosphorus insecticides are relatively unstable molecules and tendto decompose readily, particularly when exposed to high or low pH.Furthermore, organophosphorus compounds will undergo hydrolysis in thepresence of water. Thus, it is known in the prior art that the chemicalstability of solid formulations of organophosphorus insecticides can beenhanced by the addition of certain materials that reduce the rate ofchemical degradation of the active ingredient.

U.S. Pat. Nos. 4,380,537; 5,140,019; 5,165,934 and 5,260,312 alldisclose organophosphorus insecticides on solid carriers, such as clays.Specifically, U.S. Pat. No. 4,380,537 discloses an insecticideformulation containing an organophosphorus insecticide, such aschlorpyrifos, on a clay carrier, such as montmorillonite or attapulgite,and as a stabilizer for the insecticide between 0.5% and 10% by weightof a lactone. Other stabilizers of organophosphorus insecticides knownin the prior art include polyethyleneglycol and polypropyleneglycol. W.Kelley et al., "Use of Deactivators in Granular Clay Formulations,"discloses the use of ethanolamine, ethyleneglycol (and dimers thereof),propyleneglycol (and dimers thereof), and urea as deactivators forformulations of pesticides on clay-based granules. However, thestabilized insecticidal formulations of the prior art have not alwaysbeen satisfactory.

A formulation of 15% by weight chlorpyrifos on a granular clay carrierand 4.5% by weight of dipropyleneglycol as a stabilizer isunsatisfactory for agricultural use upon cold storage. After storage atrelatively cold temperatures, the granules will agglomerate and formhard lumps that make the formulation unsuitable for agriculturalapplication using conventional equipment. Heretofore, it has not beenknown how to stabilize granular formulations of organophosphorusinsecticides against agglomeration or clumping that result from coldstorage.

Therefore, a need exists for an improved cold storage stabilizedorganophosphorus insecticide formulation.

SUMMARY OF THE INVENTION

The present invention satisfies the above-described needs by providingan improved insecticidal formulation. The insecticidal formulation ofthe present invention comprises a solid carrier to which has beenapplied between approximately 2% and 40% by weight of the ultimateformulation of a nominally solid organophosphorus insecticide andbetween approximately 0.5% and 10% by weight of the ultimate formulationof a stabilizer compound selected from cyclohexanone andN-methylpyrrolidone.

Another embodiment of the present invention comprises a method of makingan insecticidal formulation. The method comprises mixing with a solidcarrier between approximately 2% and 40% by weight of the ultimateformulation of a nominally solid organophosphorus insecticide in aliquid state and between approximately 0.5% and 10% by weight of astabilizer compound selected from cyclohexanone and N-methylpyrrolidone.

Another embodiment of the present invention comprises a method of makingan insecticidal formulation comprising mixing with a solid carrier at atemperature of between approximately 30° and 200° C. betweenapproximately 2% and 40% by weight of the ultimate formulation of anominally solid organophosphorus insecticide in a liquid state andbetween approximately 0.5% and 10% by weight of the ultimate formulationof a stabilizer compound selected from cyclohexanone andN-methylpyrrolidone.

Accordingly, it is an object of the present invention to provide animproved insecticidal formulation and an improved method for making aninsecticidal formulation.

Another object of the present invention is to provide an insecticidalformulation that has improved cold storage stability.

Yet another object of the present invention is to provide aninsecticidal formulation that is flowable and resists agglomeration orclump formation upon cold storage.

These and other objects, features and advantages of the presentinvention will become apparent after a review of the following detaileddescription of the disclosed embodiments and the appended claims.

DETAILED DESCRIPTION OF THE DISCLOSED EMBODIMENTS

The present invention provides a cold storage stabilizedorganophosphorus insecticide formulation and a method of making a coldstorage stabilized organophosphorus insecticide formulation. Theorganophosphorus insecticide formulation comprises a solid carrier towhich has been applied a nominally solid organophosphorus insecticideand a stabilizer compound. In accordance with the present invention, thenominally solid organophosphorus insecticide comprises betweenapproximately 2% and 40% by weight of the ultimate formulation;preferably, between approximately 10% and 20% by weight of the ultimateformulation; especially, approximately 15% by weight of the ultimateformulation. The stabilizer compound comprises between approximately0.5% and 10% by weight of the ultimate formulation; preferably, betweenapproximately 2% and 5% by weight of the ultimate formulation. Inrelative terms, the ratio of nominally solid organophosphorusinsecticide to stabilizer compound is between approximately 80:1 and 4:1by weight.

As used herein the term "nominally solid organophosphorus insecticide"designates and means those organophosphorus insecticides that solidifywithin the temperature range at which the formulation would normally beapplied and/or stored. Generally, those temperatures at which theformulation would normally be applied and/or stored will be as low as 0°F. and as high as 110° F. Therefore, the present invention is applicableto those organophosphorus insecticides that will solidify attemperatures between approximately 0° F. and 110° F. (-17.8° and 43°C.).

The nature of the nominally solid organophosphorus insecticide is notcritical to the present invention. The only qualification is that it maysolidify at temperatures at which the formulation would normally beapplied and/or stored as defined above. The present invention isapplicable to nominally solid organophosphorus insecticides in general.Organophosphorus insecticides useful in the present invention that areclearly solids at temperatures at which the formulation would normallybe applied and/or stored include those compounds shown in Table 1 below:

                  TABLE 1                                                         ______________________________________                                        Common Name  Chemical Name                                                    ______________________________________                                        Acephate     O,S-dimethyl acetylphosphoramidothioate                          Bromophos    O-(4-bromo-2,5-dichlorophenyl) O,O-                                           dimethyl phosphorothioate                                        Chlorpyrifos O,O-diethyl O-(3,5,6-trichloro-2-pyridyl)                                     phosphorothioate                                                 Disulfoton   O,O-diethyl-S-ethylmercaptoethyl                                              dithiophosphate                                                  EPN          O-ethyl O-p-nitrophenylthiobenzene                                            phosphonate                                                      Fenamiphos   Ethyl 4-(methylthio)-m-tolyl                                                  isopropylphosphoramidate                                         Fenchlorophos                                                                              dimethyltrichlorophenylthiophosphate                             Quinalphos   O,O-diethyl O-2-quinoxalinyl                                                  phosphorothioate                                                 Trichlorfon  O,O-dimethyl-1-hydroxy-2,2,2-                                                 trichloroethylphosphonate                                        ______________________________________                                    

However, there is an additional group of organophosphorus insecticidesthat have melting points within the temperature range within which theformulation would normally be applied and/or stored. Examples of thoseorganophosphorus insecticides include those compounds shown in Table 2below:

                  TABLE 2                                                         ______________________________________                                                                        Melting                                                                       Point                                         Common Name                                                                              Chemical Name        ° C.                                   ______________________________________                                        Fenitrothion                                                                             O,O-dimethyl O-4-nitro-m-tolyl                                                                        3.4°                                           phosphorothioate                                                   Fenthion   O,O-dimethyl-O-[4-(methylthio)-m-                                                                     7.5°                                           tolyl] phosphorothioate                                            Fonofos    O-ethyl S-phenyl       32°                                             ethylphosphonothiolothionate                                       Isofenphos 1-methylethyl 2-((ethoxy((1-                                                                       -12°                                              methylethyl)amino)phosphinothioyl)                                            oxy)benzoate                                                       Pirimiphos-ethyl                                                                         O-(2-diethylamino)-6-methyl-4-                                                                       15°-18°                                  pyrimidinyl) O,O-diethyl                                                      phosphorothioate                                                   ______________________________________                                    

The preferred nominally solid organophosphorus insecticide for use inthe present invention is chlorpyrifos. Chlorpyrifos has a melting pointof between 42° and 43.5° C.

Solid carriers for organophosphorus insecticides are well known in theart and are useful in the present invention. Solid carriers that can beused in preparing the formulations of the present invention includekaolin clays, such as Kaolinite, dickite, nacrite, anauxite, halloysite,endellite and barden clay; montmorillonite clays, such as, beidellite,nontromite, montmorillonite, hectorite, saponite, savconite andbentonite; attapulgite clays, such as fuller's earth, attapulgite andsepiolite; diatomaceous earths, such as diatomite and kieselguhr; andvermiculite, such as biotite; and synthetic silicates, such as Micro-celand Silene EF, and various talcs. It is preferred that the solidcarriers used in the present invention be in a granular form suitablefor agricultural application. It is particularly preferred that thesolid carriers used in the present invention are clay carriers;especially, clay carriers selected from kaolin clays, montmorilloniteclays and attapulgite clays.

In accordance with the present invention, it has been found that a minoramount of a stabilizer compound selected from cyclohexanone andN-methylpyrrolidone when combined with the solid carrier andorganophosphorus insecticide provides a desired level of cold storagestability such that agglomeration or clumping of the cold formulation isreduced or avoided.

The formulation of the present invention is prepared by applying thenominally solid organophosphorus insecticide and the stabilizer compoundto the solid carrier, either as a mixture or separately. If appliedseparately, they can be applied in any order of addition; however, it ispreferred that the stabilizer compound be applied first. However, it ispreferred in the present invention that the organophosphorus insecticideand the stabilizer compound be applied to the solid carrier as amixture. The organophosphorus insecticide and the stabilizer compoundcan be applied to the solid carrier by any means know to those skilledin the art; however, it is preferred that they be applied by spraying.

Some nominally solid organophosphorus insecticides are solids at room orambient temperature. It is an essential feature of the present inventionthat the nominally solid organophosphorus insecticide be applied to thesolid carrier in liquid form. Therefore, for those nominally solidorganophosphorus insecticides that are solid at room or ambienttemperatures, they must be heated to their melting point. For example,chlorpyrifos is a solid at room temperature, with a melting point ofapproximately 42° C. and a boiling point of approximately 200° C.Therefore, the chlorpyrifos must be heated to a temperature betweenapproximately 42° and 200° C.; preferably, between approximately 50° and60° C. For other nominally solid organophosphorus insecticides that aresolid at room or ambient temperatures, the insecticide must be heated toa temperature above its melting point, but well below its boiling pointso that evaporation of the active insecticide is held to a minimum.

For those nominally solid organophosphorus insecticides that are liquidat room or ambient temperatures, the insecticide does not need to beheated prior to application to the solid carrier. For those nominallysolid organophosphorus insecticides that have melting points near roomor ambient temperatures, such that the insecticides are relativelythick, viscous liquids, slight heating may be required to reduce theviscosity of the insecticide before application to the solid carrier,particularly if the insecticide is to be applied to the solid carrier byspraying.

When it is necessary to heat the nominally solid organophosphorusinsecticide, the stabilizer compound should also be heated if thestabilizer compound and the insecticides are to be applied to the solidcarrier together. It is preferred that the nominally solidorganophosphorus insecticide and the stabilizer compound be applied tothe solid carrier as a mixture. Therefore, it is desirable to first meltthe nominally solid organophosphorus insecticide and then add thestabilizer compound while maintaining the temperature of the mixtureabove the melting point of the insecticide. The mixture should thereforebe maintained at a temperature between the melting point and the boilingpoint of the nominally solid organophosphorus insecticide. In the caseof chlorpyrifos, the mixture should be maintained at a temperaturebetween approximately 42° and 200° C.; preferably, between approximately50° and 60° C. The mixture should then be agitated or mixed until wellblended. The liquid mixture of insecticide and stabilizer compound isthen ready for application to the solid carrier.

When the nominally solid organophosphorus insecticide is solid at roomor ambient temperatures, i.e., the ambient temperature at which theinsecticide is to be applied to the solid carrier, in addition toheating the insecticide, it is necessary to heat the solid carrier to atemperature between the melting point of the insecticide and the boilingpoint of the insecticide ; i.e., generally between approximately 30° and300° C. Heating the solid carrier prevents the insecticide from freezingon the surface of the solid carrier when the insecticide contacts thecarrier. Heating also facilitates penetration of the nominally solidorganophosphorus insecticide and stabilizer compound into the solidcarrier. For example, for chlorpyrifos, the solid carrier should beheated to a temperature between approximately 42° and 200° C.;preferably, between approximately 65° and 75° C. The solid carrier canbe preheated using any suitable means to obtain the specifiedtemperature. Heating can be accomplished with a jacketed blender, steamcoils, contact heaters or fluidized beds.

When the nominally solid organophosphorus insecticide is liquid at roomor ambient temperatures, heating of the solid carrier prior toapplication of the stabilizer compound may not be required.

Any suitable means known to those skilled in the art can be used toapply the nominally solid organophosphorus insecticide and stabilizercompound to the carrier and to mix the materials together. A commonlyused device is a tumbling-type mixer made by Munson Machinery Company.Generally, the clay is weighed, preheated and charged to the blender.The insecticide/stabilizer mixture is then sprayed onto the clay using aspray nozzle inside the blender to evenly distribute the liquid onto theclay. Blending of the clay is continued after completion of the liquidaddition until a uniform mixture is obtained.

The following examples are illustrative of the present invention and arenot intended to limit the scope of the invention as set forth in theappended claims. All temperatures are in degrees Celsius and allpercentages are by weight unless specifically stated otherwise.

EXAMPLE 1

The formulation shown in Table 3 below was prepared:

                  TABLE 3                                                         ______________________________________                                        Ingredient  Wt. % of Ultimate Formulation                                                                    Weight (lbs)                                   ______________________________________                                        Agsorb LVM 24/48                                                                          80.0               8,000                                          clay granules*                                                                chlorpyrifos                                                                              15.5               1,550                                          technical (98%)                                                               cyclohexanone                                                                             4.5                450                                            TOTAL       100.0              10,000                                         ______________________________________                                         *Agsorb LVM 24/48 clay granules are montmorillonite clay granules             available from OilDri Corporation of America of Chicago, Illinois.       

The Agsorb granules were weighted and then heated to a temperature ofbetween 65° and 71° C. The heated solid carrier granules were thentransferred to a Munson blender. Technical chlorpyrifos (98% by weight)was melted by storing the technical material in a water bath at 50°-55°C. The melted technical material was then pumped into a mixing tankequipped with an agitator and a hot water jacket to maintain thecontents of the tank at a temperature of 50°-55° C. Cyclohexanone wasadded to the mixing tank and agitated until well mixed. The blender wasstarted and the chlorpyrifos/cyclohexanone mixture was sprayed under apressure of 30 psi onto the surface of the tumbling clay. Two fan-typespray nozzles were used to atomize the chlorpyrifos/cyclohexanonemixture. Spraying time was 8 minutes. Blending continued for another 10minutes after spraying of the chlorpyrifos/cyclohexanone mixture wascompleted. The product was transferred from the blender into a packaginghopper where it was then packed in plastic bags that held 50 pounds ofthe chlorpyrifos/cyclohexanone/clay formulation.

EXAMPLE 2

The formulation shown in Table 4 below was prepared in accordance withthe procedure described above in Example 1:

                  TABLE 4                                                         ______________________________________                                        Ingredient  Wt. % of Ultimate Formulation                                                                    Weight (lbs)                                   ______________________________________                                        Agsorb LVM 24/48                                                                          82.0               8,200                                          clay granules                                                                 chlorpyrifos                                                                              15.5               1,550                                          technical (98%)                                                               cyclohexanone                                                                             2.5                250                                            TOTAL       100.0              10,000                                         ______________________________________                                    

The chlorpyrifos/cyclohexanone/clay formulation was also packaged inplastic bags containing 50-pound of the formulation.

EXAMPLE 3

The formulation shown in Table 5 below was prepared in accordance withthe procedure described above in Example 1, except that dipropyleneglycol was substituted for cyclohexanone:

                  TABLE 5                                                         ______________________________________                                        Ingredient  Wt. % of Ultimate Formulation                                                                    Weight (lbs)                                   ______________________________________                                        Agsorb LVM 24/48                                                                          80.0               8,200                                          clay granules                                                                 chlorpyrifos                                                                              15.5               1,550                                          technical (98%)                                                               dipropylene glycol                                                                        4.5                450                                            TOTAL       100.0              10,000                                         ______________________________________                                    

The chlorpyrifos/dipropylene glycol/clay formulation was also packagedin plastic bags containing 50-pounds of the formulation.

EXAMPLE 4

The formulation shown in Table 6 below was prepared in accordance withthe procedure described above in Example 1, except thatN-methylpyrrolidone was substituted for cyclohexanone:

                  TABLE 6                                                         ______________________________________                                        Ingredient  Wt. % of Ultimate Formulation                                                                    Weight (lbs)                                   ______________________________________                                        Agsorb LVM 24/48                                                                          80.0               8,200                                          clay granules                                                                 chlorpyrifos                                                                              15.5               1,550                                          technical (98%)                                                               N-methylpyrrolidone                                                                       4.5                450                                            TOTAL       100.0              10,000                                         ______________________________________                                    

The chlorpyrifos/dipropylene glycol/clay formulation was also packagedin plastic bags containing 50-pound of the formulation.

EXAMPLE 5

A refrigerated storage chamber was constructed for evaluating coldstability of test batches of the chlorpyrifos 15% granular insecticideformulations prepared in Examples 1-4 above. The chamber was largeenough to store full pallets of product. Fifty-pound bags from each ofthe four test batches and 50 pound bags of Lorsban 15G manufactured byDow Agrosciences of Indianapolis, Ind., were stacked in an alternatingpattern to make up composite test pallets. Each pallet contained a totalof 2,500 pounds of the four test formulations and Lorsban 15G; i.e., 10bags of each of the four test formulations and 10 bags of Lorsban 15G.The composite pallets were transferred to the cold storage chamber withanother full pallet containing 2,500 pounds placed on top of the testpallet to provide a compacting force during storage. At the intervalslisted in Table 7 below, a test pallet was removed from cold storage andthe bags were opened and evaluated by pouring the contents across a meshscreen with 1/4 inch openings. Temperature probes were installed in thecold storage chamber and probes were inserted into bags on the testpallets. On days 2 and 3, the bag temperatures were between 27° and 36°F. (-2.8° and 2.2° C.). For the 7 and 14 day evaluation, the bagtemperatures were between 10° and 21° F. (-12.2° and -6.1° C.).

Product aggregation or clumping was determined by estimating the lumberof lumps observed while emptying each bag across the screen and notingwhether the lumps were hard or soft. Soft lumps would either break apartby contact with the screen or by gentle movement of the screen. Hardlumps were not broken up by contact with or movement of the screen. Thecold storage results are shown in Table 7 below.

                  TABLE 7                                                         ______________________________________                                        Days in                                Lorsban                                Storage                                                                             Example 1                                                                              Example 2                                                                              Example 3                                                                             Example 4                                                                            15G                                    ______________________________________                                        2     0            1 soft >20 hard                                                                              0      10   soft                            3     0            1 soft >20 hard                                                                              0      6    soft                            7     5     soft   1 soft >20 hard                                                                              0      >20  hard                            14    5     soft   3 soft >20 hard                                                                              0      >20  hard                            ______________________________________                                    

The test data shows that the materials made in accordance with thepresent invention using cyclohexanone and N-methylpyrrolidone; i.e.,Examples 1, 2 and 4, had significantly better cold storage stabilitythan either the product made using propylene glycol; i.e., Example 3, orthe commercial product Lorsban 15G.

It should be understood, of course, that the foregoing relates only tocertain disclosed embodiments of the present invention and that numerousmodifications or alterations may be made therein without departing fromthe spirit and scope of the invention as set forth in the appendedclaims.

What is claimed is:
 1. In a solid cold stabilized insecticidalformulation that comprises from about 2% to about 40% by weight of anominally solid organophosphorus insecticide, a solid granular claycarrier therefor, and a cold stabilizing amount of a stabilizer compoundfor said formulation, the improvement in said formulation whichcomprises using as the stabilizer compound, from about 0.5% to about 10%by weight of the ultimate formulation of a compound selected fromcyclohexanone and N-methylpyrrolidone.
 2. A composition comprising asolid carrier to which has been applied a mixture, said mixturecomprising between approximately 2% and 40% by weight of the ultimatecomposition of a nominally solid organophosphorus insecticide andbetween approximately 0.5% and 10% by weight of a stabilizer compoundselected from cyclohexanone and N-methylpyrrolidone.
 3. The compositionof claim 2, wherein said solid carrier is selected from kaolin clays,montmorillonite clays, attapulgite clays, diatomaceous earths,vermiculites, synthetic silicates, and talcs.
 4. The composition ofclaim 2, wherein said stabilizer compound is present in an amountbetween approximately 2% and 5% by weight of the ultimate composition.5. The composition of claim 2, wherein said organophosphorus insecticideis chlorpyrifos.
 6. The composition of claim 2, wherein saidorganophosphorus insecticide is selected from Acephate, Bromophos,Chlorpyrifos, Disulfoton, EPN, Fenamiphos, Fenchlorophos, Quinalphos,Trichlorfon, Fenitrothion, Fenthion, Fonofos, Isofenphos, andPirimiphos-Ethyl.
 7. A composition comprising a solid granular claycarrier to which has been applied between approximately 10% and 20% byweight of the ultimate composition chlorpyrifos and betweenapproximately 2% and 5% by weight of the ultimate composition of astabilizer compound selected from cyclohexanone and N-methylpyrrolidone.8. The composition of claim 7, wherein said stabilizer compound iscyclohexanone.
 9. The composition of claim 7, wherein said stabilizercompound is N-methylpyrrolidone.
 10. The composition of claim 7, whereinsaid clay carrier is selected from kaolin clays, montmorillonite clays,and attapulgite clays.
 11. The composition of claim 7, wherein saidsolid carrier is attapulgite.
 12. The composition of claim 7, whereinsaid solid carrier is montmorillonite.
 13. A method comprising the stepsof:applying to a solid granular clay carrier between about 2% and about40% by weight of a nominally solid organophosphorus insecticide in aliquid state and between approximately 0.5% and 10% by weight of astabilizer compound selected from cyclohexanone and N-methylpyrrolidone,said clay carrier being at a temperature of between approximately 30°and 200° C.; mixing the organophosphorus insecticide, stabilizercompound and clay carrier to form a substantially uniform mixture; andpermitting said mixture to cool to ambient temperature.
 14. The methodof claim 13, wherein said clay carrier is selected from kaolin clays,montmorillonite clays, and attapulgite clays.
 15. The method of claim13, wherein said stabilizer is present in an amount from about 2% toabout 5% by weight of the ultimate composition.
 16. The method of claim13, wherein said nominally solid organophosphorus insecticide ischlorpyrifos.
 17. The method of claim 13, wherein said nominally solidorganophosphorus insecticide is selected from the group of Acephate,Bromophos, Chlorpyrifos, Disulfoton, EPN, Fenamiphos, Fenchlorophos,Quinalphos, Trichlorfon, Fenitrothion, Fenthion, Fonofos, Isofenphos,and Pirimiphos-Ethyl.
 18. A method comprising mixing with a clay carrierat a temperature of between approximately 30° and 200° C. betweenapproximately 2% and 40% by weight of a nominally solid organophosphorusinsecticide in a liquid state and between approximately 0.5% and 10% byweight of a stabilizer compound selected from cyclohexanone andN-methylpyrrolidone.
 19. The method of claim 18, wherein said claycarrier is selected from kaolin clays, montmorillonite clays, andattapulgite clays.
 20. The method of claim 18, wherein said stabilizeris present in an amount from about 2% to about 5% by weight of theultimate composition.
 21. The method of claim 18, wherein said nominallysolid organophosphorus insecticide is chlorpyrifos.
 22. The method ofclaim 18, wherein said nominally solid organophosphorus insecticide isselected from the group of Acephate, Bromophos, Chlorpyrifos,Disulfoton, EPN, Fenamiphos, Fenchlorophos, Quinalphos, Trichlorfon,Fenitrothion, Fenthion, Fonofos, Isofenphos, and Pirimiphos-Ethyl. 23.The method of claim 18, wherein said stabilizer compound iscyclohexanone.
 24. The method of claim 18, wherein said stabilizercompound is N-methylpyrrolidone.
 25. The method of claim 18, whereinsaid clay carrier is montmorillonite.
 26. The method of claim 18,wherein said clay carrier is attapulgite.
 27. A composition comprising anominally solid organophosphorus insecticide and a stabilizer compoundselected from cyclohexanone and N-methylpyrrolidone, the ratio ofnominally solid organophosphorus insecticide to stabilizer compoundbeing between approximately 80:1 and 4:1.
 28. A method comprising thesteps of:applying to a solid granular clay carrier between about 2% andabout 40% by weight of chlorpyrifos in a liquid state and betweenapproximately 0.5% and 10% by weight of a stabilizer compound selectedfrom cyclohexanone and N-methylpyrrolidone, said clay carrier being at atemperature of between approximately 150° and 160° F.; mixing thechlorpyrifos, stabilizer compound and clay carrier to form asubstantially uniform mixture; and permitting said mixture to cool toambient temperature.
 29. A method comprising mixing with a clay carrierat a temperature of between approximately 150° and 160° F. betweenapproximately 2% and 40% by weight of a nominally solid organophosphorusinsecticide in a liquid state and between approximately 0.5% and 10% byweight of a stabilizer compound selected from cyclohexanone andN-methylpyrrolidone.